Among modern electronic timepieces, electronic timepieces that have therein systems for displaying a plurality of kinds of functions, including a chronographic display function, alarm display function, atmospheric pressure display function, sounding display function, temperature display function, etc. have started to be put to practical use, and are configured so that one or a plurality of kinds of function information is displayed simultaneously with or alternatively to time information on specific display means.
Conventionally, on the other hand, some known electronic timepieces additionally have a power-saving mode function that serves to lower the power consumption of the electronic timepiece unless it constitutes any special hindrance to the use of the electronic timepiece, in order to maximize the durability of power source means that is composed of a battery or an accumulator used in combination with power generating means.
As is described in Japanese Patent Application Laid-Open No. 61-77788, for example, an electronic timepiece is known that has a solar cell as its main power source and is constructed so that a power-saving mode is established to lower its power consumption if the sunlight is not incident upon a solar cell of the electronic timepiece for a predetermined fixed continuous time, and that the power-saving mode is canceled when the sunlight is incident again upon the solar cell.
The power-saving mode function of this conventional electronic timepiece is designed so that the power-saving mode is established to stop the display of time information if the power source is in an unfavorable situation or if the solar cell as the power source is used in the dark, for example.
Although both the power-saving mode function and the function information operation state mode serve to improve the commercial value of the electronic timepiece, they may possibly interfere with each other, so that the drive of the respective operations of the two functions requires adjustment.
If the display function for function information is activated when the environment of power generation or the level of charge is lowered, for example, the battery is consumed by power that is required by the display of the function information, so that the original time display function of the electronic timepiece may possibly be stopped.
Further, some known rechargeable electronic timepieces are designed so that information on the state of the power source of the watch and the past history of stoppage can be given to a user of the watch and that trouble caused as the watch run-down due to undercharge can be avoided to the utmost. Described in Japanese Patent Application Laid-Open No. 62-194484, for example, is an electronic timepiece, in which normal operation (one-second-step movement) is performed if the charge level (supply voltage) of the power source is adequate, first modulated hand movement operation (two-second-step movement) as a charge warning is performed if the charge level is about to fail, and second modulated hand movement operation as a run-down state warning, modulated differently from the first modulated hand movement operation, is performed to warn the user of the past history of a run-down state (and therefore, wrongness of indicated time) despite later recovery of the charge level and restart of the hand movement if the charge level is so low that the watch is stopped, whereby two types of warning display are performed. Also known is an electronic timepiece that performs residue warning information display such that the residual capacity (residue) of a battery is indicated by the movement of a pointer. Described in Japanese Patent Application Laid-Open No. 55-22153, for example, is an electronic timepiece that displays residue warning information in accordance with the movement of a pointer in a residue warning display monitor mode based on switch operation.
If the hand movement operation is stopped so that the display is stopped in a power-saving state, warning information also ceases to be displayed, so that the electronic timepiece inevitably cannot fulfill its function, as in the case of the aforementioned invention described in Japanese Patent Application Laid-Open No. 61-77788. The warning information, in particular, is information that is related to the state of the power source, and is generated when the supply voltage is lowered if accumulator means is undercharged by power generating means. The same applies to the aforementioned residue warning display of Japanese Patent Application Laid-Open No. 55-22153. Further, the power-saving function, especially in a rechargeable electronic timepiece, is a function that is required when the accumulator means is undercharged. The warning display is needed with high possibility in a state that requires power-saving operation.
Accordingly, a first object of the present invention is to provide an electronic timepiece having both of functions for function display operation and power-saving operation and a driving method for the electronic timepiece, and to provide an electronic timepiece with high commercial value, which is configured to be able to use separately a power-saving mode function that entails lower power consumption and a function information operation state mode that provides many kinds of additional function information, and a driving method for the electronic timepiece.
Further, a second object of the present invention is to provide an electronic timepiece, in which display of a power-saving state and warning information is optimally controlled so that the electronic timepiece can fulfill its function, and a control method therefor.